Metal processing



Dec. 13, 1966 R. F. HARVEY 3,290,936

METAL PROCESSING Filed Sept. 5, 1962 2 Sheets-$heet l FORGE {my x70 INVENTOR.

Dec. 13, 1966 R. F. HARVEY METAL PROCESSING 2 Sheets-Sheet z Filed Sept. 5, 1962 Jay M United States Patent 3,290,936 t. METAL PROCESSING Richard F. Harvey, Dorseyville, Pa., assignor to Metaltronics, Inc, Pittsburgh, Pa. Filed Sept. 5, 1962, Ser. No. 221,611 15 Claims. (Cl. 72-203) This invention relates to improvements in metal making practices. More particularly this method involves cross rolling barstock to result in a degree of uniformity of structure and distribution of carbides and segregate which represents a marked improvement over conventional metal working practice.

In conventional steel making methods used in making barstock, it is general practice to press, roll, or hammer cog the cast ingots to reduce their cross sectional area and to extend their length. The product of this operation is termed a billet. The billets may be further reduced to a smaller billet and the finishing operations commonly involve rolling to a bar of the desired shape. In the conventional steel mill operations for making barstock the steel is worked in the same direction in the various steps resulting in marked directionality or anisotropy. This results in elongation of the grains, alloy segregate, and carbides in the direction of Working. As a result the mechanical properties vary along the direction of working as compared with across the direction of Working. This is particularly true of the highly-alloyed steel such as the high speed steels.

High carbon-high chromium tool steel of the D-2 type shows a longitudinal unnotched Izod toughness value which is three times greater than the transverse values according to the Metals Handbook, vol. 1, Properties and Selection of Metals, 8th edition, 1961, p. 649. Size change on heat treatment also varies with the direction of fibre, the change being greater when measured along the direc' tion of working rather than across the direction of workmg.

Working metals in one direction has a tendency to elongate rather than break up the highly segregated, cast structure characteristic of ingots.

On highly alloyed steels such as high speed steel used for cutting tools, the cast condition is a highly segregated, cored, network structure which is recognized as being very undesirable. The need to break up this structure to as great an extent as possible is recognized, but the prior art methods are relatively ineffective in producing a high degree of uniformity in barstock principally because the methods in use work the steel in the same direction and tend merely to elongate rather than break up the carbide and segregate.

My investigations confirm the experience of others insofar as the harmful effects of directional properties and directional segregation is concerned. However, the present invention teaches a novel, practical, highly effective meth- 0d of producing barstock with a high degree of uniformity and absence of the directional effects characteristic of barstock produced by prior art methods.

The essential feature of the present invention involves cross rolling a bar from a billet in which the grain or directional properties run across rather than lengthwise with the billet. To accomplish this result a cast ingot is cogged to a large billet preferably rectangular in cross section. A smaller billet is then cut from the large billet so that the directional properties or grain run across the length of the cut smaller billet and not along the length of the billet as in conventional practice. The cut smaller billet may then be further reduced or it may be rolled to a finish size bar. In this manner the bar is cross rolled resulting in a highly effective means of breaking up and minimizing the directional segregate and providing a high degree of uniformity with appreciably little difference in the structure and properties along and across the axis of the bar.

The first billet produced from the cast ingot will be designated as a first stage billet and this billet is preferably made in the conventional manner with directional properties extending lengthwise with the billet.

The smaller billet, which is cut from the first stage billet so that the directional properties or grain run across rather than lengthwise with the billet, will be designated as a cross grained second stage billet in this specification.

Similarly further stages of billet reduction will be designated as cross grained third stage billet, cross grained fourth stage billet, etc.

Barstock characterized by a high degree of uniformity in stucture and physical properties is rolled from a cross grained billet in accordance with the teachings of the pres ent invention.

It is important also that an optimum reduction be used from ingot to finished bar and from cross grained second stage billet to finished bar as Will be explained in further detail hereinafter.

It is an object of this invention to provide a means for making barstock of metals which are characterized by a high degree of uniformity both along and across the axis of the bar.

It is a further object of this invention to provide a means for making barstock from highly alloyed metals which are characterized by a uniform distribution of the segregate and carbides.

It is a related object of this invention to provide a means of producing barstock in which the grain or directional properties are held to a minimum.

It is also an important object of this invention to provide a method for producing barstock in which the mechanical properties and in particular the ductility are substantially the same as determined across and along the length of the bar.

These and other objects will be apparent from the specifications and examples which follow. While the invention will be described in conjunction with the following example, it should be understood that the details are not to be construed as limiting the invention.

EXAMPLE I An M2 high speed steel of the following typical analysis was used in one embodiment of the present invention:

Percent Carbon 0.85 Tungsten 6.50 Molybdenum 5.00 Chromium 4.00 Vanadium 2.00

Referring to FIGURE 1, a 15 inch square ingot 1 of the M2 high speed steel was cogged to a 9 /2 in. x 16 in. first stage billet 2. The direction of grain or working is illustrated by the arrows 3.

A cross grained, second stage billet 4 which measured 9 /2 in. X 9 /2 in. X 16 in. was cut from the first stage billet 2. It will be noted that the direction of grain or working, as indicated by the arrows 3 is across the length or axis of the second stage billet 4. The cross grained second stage billet 4 which measured 9 /2 in. X 9 /2 in. X 16 in. was further reduced by forging to a cross grained third stage billet 5 which measured 4% in. square in cross sectional area. It will be noted also that this billet 5 is cross grained and the direction of grain and Working, as indicated by the arrows 3 is predominently across the length of the third stage billet 5.

In the final operation, the cross grained third stage billet is rolled to a 3% in. diameter bar 6. The cross sectional reduction from ingot to finished bar was about 27 to 1 and the cross sectional reduction from cross grained second stage billet to finished bar was about to l.

The 3 /4 in. round bar 6 made in accordance with the principles of the present invention had a longitudinal microstructure as determined in the annealed condition, which is illustrated in FIGURE 2 at 100X. The photomicrograph illustrates the longitudinal structure at the center of the bar. However this structure is typical of all sections of the bar from the surface to the center and from one end of the bar to the other.

By comparison FIGURE 3 at IOOX illustrates the longitudinal structure in the annealed condition of the center of a 3% inch round bar of the same grade of steel and made from the same size ingot by conventional practice.

In the example cited three different size billets were employed. This however is an operational detail which is not or" critical importance. In some cases one or two cross grained billet sizes are employed and in others there may be four or more. The important consideration is that a cross grained billet be employed and that the rolling of the cross grained billet be done under optimum conditions of reduction to effect a substantial degree of uniformity and absence of segregation and directional effects.

In practicing the present invention I have found there is an optimum reduction from ingot to finished bar and from the cross grained second stage billet to finished bar. The ingot size is taken as the average between the large and small ends of the ingot.

My investigations show that the ratio of the cross sectional ingot area to the cross sectional area of the rolled barstock should be less than about 60:1 and preferably this should be less than 40: 1. However, in any case the ratio of the cross sectional ingot area to the cross rolled barstock should be greater than 5: 1.

My investigations also show that the ratio of the cross sectional area of the cross grained second stage billet to the cross sectional area of the rolled barstock should be less than about 18:1 and preferably this should be less than 12:1. However in any case, the ratio of the cross sectional area of the cross grained second stage billet to the cross sectional area of the rolled barstock should be greater than 2 /2 1.

The superiority of barstock made in accordance with the teachings of the present invention as illustrated in FIGURE 2 will be readily apparent to those skilled in metallurgy. A comparison of the longitudinal structure of bars made by the present invention and illustrated in FIGURE 2 represent a pronounced improvement over the conventional and prior art methods represented by FIGURE 3.

The comparison illustrated was taken at its center. Conventionally processed bars have a center structure which is characteristically poor. Also a comparison of barstock made by the present invention with conventional practice would result in greater differences in structure for the larger diameters. In fact the present invention teaches the manufacture of large diameter barstock up to about 10 inches in diameter with greatly minimized segregation and directional properties.

Barstock in diameters as large as 10 inches in diameter have a very poor metallurgical structure when made by conventional practice and for this reason it is common practice to specify forgings in the larger sizes. The present invention extends the useful range of barstock to larger diameters than has heretofore been thought to be practical with savings in inventory and cost as compared with forgings. Also relatively long sections of large diameter for such applications as broaches, Sendzinir rolls etc. require the use of large diameter barstock which can best be made by the teachings of the present invention.

Also barstock made by the present invention has been found to result in reduced amounts of distortion and size change on heat treating. This is thought to be due to the uniformity of structure and minimized directional effects.

While I have described several preferred embodiments of this invention, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

I claim:

l. The process of cross rolling high alloy metal barstock which consists in first cogging a cast ingot to reduce its cross sectional area to a first stage billet; then cutting a smaller cross grained second stage billet from the first stage billet, said cross grained second stage billet being cut so that the direction of working is across rather than along the length of the cross grained second stage billet; and finally rolling the second stage billet to a bar, the ratio of the cross sectional area of the ingot to the cross sectional area of the bar being less than about :1 and greater than 5:1.

2. The process of cross rolling high alloy metal barstock substantially as described in claim 1 wherein the ratio of the cross sectional area of the ingot to the cross sectional area of the bar is less than 40:1 and greater than 5:1.

3. The process of cross rolling high alloy metal barstock which consists in first cogging a cast ingot to reduce its cross sectional area to a first stage billet; then cutting a smaller cross grained second stage billet from the first stage billet, said cross grained second stage billet being cut so that the direction of Working is across rather than along the length of the cross grained, second stage billet; and finally rolling the second stage billet to a bar, the ratio of the cross sectional area of the cross grained second stage billet to the cross sectional area of the bar being less than about 18:1 and greater than 2%.:1.

4. The process of cross rolling high alloy metal barstock substantially as described in claim 2 wherein the ratio of the cross sectional area of the cross grained, second stage billet to the cross sectional area of the bar being less than 12:1 and greater than 2 /2:1.

5. In rolling high alloy metal barstock the step of cross rolling a billet wherein the ratio of the area of the cross grained billet to the cross sectional area of the bar is less than about 18:1 and greater than 2 /2:1.

6. In rolling high alloy metal barstock the step of cross rolling a billet wherein the ratio of the area of the cross grained billet to the cross sectional area of the bar is less than 12:1 and greater than 2 /2:1.

7. An improved method of making high alloy metal barstocks characterized by a high degree of uniformity of carbide distribution and absence of segregation which consists in rolling a bar from a cross grained billet, the reduction in area from the cross grained billet to bar being less than 18:1 and greater than 2 /2: 1.

8. The process of cross rolling high alloy metal barstock to minimize segregation and directional efi'ects therein, which consists in first cogging a cast ingot to a first stage billet, said first stage billet having a direction of Working which is along the length of the billet; and then cutting a smaller cross grained, second stage billet from the first stage billet, said second stage billet being cut so that the directional properties or gain is across the length of the said cross grained second stage billet; and finally reducing the said second stage billet to a bar by extending the said second stage billet lengthwise, wherein the ratio of the area of the cross grained second stage billet to the ratio of the area of the bar is less than about 18 to l and is greater than about 2% to 1. a

9. The process of cross rolling high alloy metal. barstock to minimize segregation and directional effects therein which consists in first cogging a cast ingot to a first stage billet, said first stage billet having a direction of Working along the length of the billet; and then cutting a smaller, cross grained, second stage billet from the first stage billet, said second stage billet being cut so that the directional properties or grain is across the length of the said second stage billet; and finally reducing the second stage billet to extend its length and to reduce it to a bar wherein the cross sectional area reduction from ingot to bar is less than about 60 to 1 and is greater than about 5 to 1.

10. The process substantially as described in claim 9 wherein the cross sectional reduction in area from ingot to bar is less than about 40 to 1 and is greater than about 5 to 1.

11. The process substantially as defined in claim 9 wherein the cross sectional reduction in area from ingot to bar is less than about 60 to 1 and is greater than about 5 to 1, and wherein the cross sectional reduction in area from the cross grained second stage billet to the finished bar is less than about 18 to 1 and is greater than about 2 /2 to 1.

12. The process substantially as defined in claim 9 wherein the cross sectional reduction in area from ingot to bar is less than about 40 to 1 and is greater than about 5 to 1, and wherein the cross sectional reduction in area from the cross grained second stage billet to the finished bar is less than about 12 to 1 and is greater than about 2 /2 to 1.

13. The process of cross rolling high speed steel barstock which consists in first cogging a cast ingot to a first stage billet, said billet being reduced in cross section and being elongated so that the direction of working is along the length of the billet; cutting a smaller, cross grained, second stage billet from the first stage billet, said second stage billet being cut so that its direction of working is across its length; and finally reducing the second stage, cross grained billet to a bar, said second stage, cross grained billet being reduced in cross section and being elongated so that the direction of working is along the length of the billet, the cross sectional reduction in area from the cross grained, second stage billet to the finished bar being less than about 18 to 1 and being greater than 5 about 2 /2 to 1.

14. The process substantially as described in claim 13 wherein the cross sectional reduction from the cross grained, second stage billet to bar is less than about 12 to 1 and is greater than about 2 /2 to 1.

15. The process of cross rolling high speed steel barstock to minimize segregation and directional efiects therein, which consists in first cogging a cast ingot to a first stage billet, said first stage billet having a direction of working which is along the length of the said billet; and then cutting a smaller second stage billet from the first stage billet, said second stage billet being cut so that the directional properties or grain is across the length of the said second stage billet; and finally reducing the said cross grained second stage billet to a bar by extending the said second stage billet lengthwise, and employing a cross sectional reduction in area from ingot to finished bar of about 27 to 1 and from cross grained, second stage billet to finished bar of about to 1.

References Cited by the Examiner UNITED STATES PATENTS 691,565 1/ 1902 Norton. 1,483,451 2/1924 Kenney. 1,567,961 12/1925 Lauren SO-63 OTHER REFERENCES JOHN F. CAMPBELL, Primary Examiner.

J. D. HOBART, Assistant Examiner. 

9. THE PROCESS OF CROSS ROLLING HIGH ALLOY METAL BARSTOCK TO MINIMIZE SEGREGATION AND DIRECTIONAL EFFECTS THEREIN WHICH CONSISTS IN FIRST COGGING A CAST INGOT TO A FIRST STAGE BILLET, SAID FIRST STAGE BILLET HAVING A DIRECTION OF WORKING ALONG THE LENGTH OF THE BILLET; AND THEN CUTTING A SMALLER, CROSS GRAINED, SECOND STAGE BILLET FROM THE FIRST STAGE BILLET, SAID SECOND STAGE BILLET BEING CUT SO THAT THE DIRECTIONAL PROPERTIES OR GAIN IS ACROSS THE LENGTH OF THE SAID SECOND STAGE BILLET; AND FINALLY REDUCING THE SECOND STAGE BILLET TO EXTEND ITS LENGTH AND TO REDUCE IT TO A BAR WHEREIN THE CROSS SECTIONAL AREA REDUCTION FROM INGOT TO BAR IS LESS THAN ABOUT 60 TO 1 AND IS GREATER THAN ABOUT 5 TO
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